Equivalent of SQL Isnull in Linq

Equivalent of SQL ISNULL in LINQ?

Since aa is the set/object that might be null, can you check aa == null ?

(aa / xx might be interchangeable (a typo in the question); the original question talks about xx but only defines aa)

i.e.

select new {
    AssetID = x.AssetID,
    Status = aa == null ? (bool?)null : aa.Online; // a Nullable<bool>
}

or if you want the default to be false (not null):

select new {
    AssetID = x.AssetID,
    Status = aa == null ? false : aa.Online;
}

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Update; in response to the downvote, I've investigated more... the fact is, this is the right approach! Here's an example on Northwind:

        using(var ctx = new DataClasses1DataContext())
        {
            ctx.Log = Console.Out;
            var qry = from boss in ctx.Employees
                      join grunt in ctx.Employees
                          on boss.EmployeeID equals grunt.ReportsTo into tree
                      from tmp in tree.DefaultIfEmpty()
                      select new
                             {
                                 ID = boss.EmployeeID,
                                 Name = tmp == null ? "" : tmp.FirstName
                        };
            foreach(var row in qry)
            {
                Console.WriteLine("{0}: {1}", row.ID, row.Name);
            }
        }

And here's the TSQL - pretty much what we want (it isn't ISNULL, but it is close enough):

SELECT [t0].[EmployeeID] AS [ID],
    (CASE
        WHEN [t2].[test] IS NULL THEN CONVERT(NVarChar(10),@p0)
        ELSE [t2].[FirstName]
     END) AS [Name]
FROM [dbo].[Employees] AS [t0]
LEFT OUTER JOIN (
    SELECT 1 AS [test], [t1].[FirstName], [t1].[ReportsTo]
    FROM [dbo].[Employees] AS [t1]
    ) AS [t2] ON ([t0].[EmployeeID]) = [t2].[ReportsTo]
-- @p0: Input NVarChar (Size = 0; Prec = 0; Scale = 0) []
-- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 3.5.30729.1

QED?

ISNULL equivalent in Linq

You can use ?? operator instead of ISNULL:

Table.Where(t=> (t.IsActive ?? false) == act);

How to write SQL IsNull() in Linq?

var InvoiceNo = dbContext.Sales.Max(x => (int?)x.InvoiceNo) ?? 0;

Linq to Sql isnull in where clause not working

just use the coalesce ?? operator

where

(tesrt.EH_PP_TESRT_TeacherEvalStatusID  ?? 0) == 1

or if it's a string (not really clear with your code)

(tesrt.EH_PP_TESRT_TeacherEvalStatusID  ?? "0") == "1"

But with the sample code given, this seem to be useless (the first version should do the same).

If what you mean is

take all values where tesrt.EH_PP_TESRT_TeacherEvalStatusID IS NULL or
tesrt.EH_PP_TESRT_TeacherEvalStatusID == 1

then

tesrt.EH_PP_TESRT_TeacherEvalStatusID == null || tesrt.EH_PP_TESRT_TeacherEvalStatusID == 1

or

tesrt.EH_PP_TESRT_TeacherEvalStatusID ?? 1 == 1

Using ISNULL on an int? in the WHERE clause of Linq queries

Why not simply:

var q = ctx.Projects.Where(p => p.ParentId == parentId);

That works if parentId is an int or int?.

If you treat the null as 0 this should work:

 var q = ctx.Projects.Where(p => (p.ParentId ?? 0) == parentId);

Select IsNull in Linq

You can try the below (have not been able to test, maybe will require some adjustments, but should be in the same form);

from Doc in db.document 
join DocDef in db.qryDocumentDefinitions on doc.documentDefId equals DocDef.documentDefId 
join Cus in db.Customer on Cus.customerId = Doc.customerId
from loan in db.loan 
     .Where(loan => loan.loanId == Doc.loanId).DefaultIfEmpty()
select new
    {
         CustNo= Cus.customerNumber
        ,loan == null ? "" : loan.loanNumber
        ,DocType= DocDef.documentTypeName
        ,DocSubType= DocDef.documentSubTypeName
        ,filename = Doc.filename
        ,inputType = (?int)(from Sys in db.SystemProperties 
                              where Sys.propertyKey.Contains("acculoan.inputType.Other")
    }

Entity Framework ISNULL in Where condition

Try something like

MyTable.Where( t => (t.Status ?? "") == "CO" )

Linq to Sql IsNull replacing NULL FK with existing FK

Have you tried VB's binary if() operator?

from baseOne in BaseOne _
join m in M on if(baseOne.MChildID,baseOne.MID) equals m.ID _
select baseOne,m

It produces a COALESCE, which is similar to ISNULL.

FROM [BaseOne] AS [t0]
INNER JOIN [M] AS [t1] ON (COALESCE([t0].[MChildID],[t0].[MID])) = [t1].[ID]

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